Many businesses and other facilities, such as banks, stores, airports, etc., make use of security systems. Among such systems are video-based systems, in which a sensing device, like a video camera, obtains and records images within its sensory field. For example, a video camera will provide a video record of whatever is within the field-of-view of its lens. Such video images may be monitored by a human operator and/or reviewed later by a human operator. Recent progress has allowed such video images to be monitored also by an automated system, improving detection rates and saving human labor.
One common issue facing designers of such security systems is the tradeoff between the number of sensors used and the effectiveness of each individual sensor. Take for example a security system utilizing video cameras to guard a large stretch of site perimeter. On one extreme, few wide-angle cameras can be placed far apart, giving complete coverage of the entire area. This has the benefit of providing a quick view of the entire area being covered and being inexpensive and easy to manage, but has the drawback of providing poor video resolution and possibly inadequate detail when observing activities in the scene. On the other extreme, a larger number of narrow-angle cameras can be used to provide greater detail on activities of interest, at the expense of increased complexity and cost. Furthermore, having a large number of cameras, each with a detailed view of a particular area, makes it difficult for system operators to maintain situational awareness over the entire site.
Common systems may also include one or more pan-tilt-zoom (PTZ) sensing devices that can be controlled to scan over wide areas or to switch between wide-angle and narrow-angle fields of view. While these devices can be useful components in a security system, they can also add complexity because they either require human operators for manual control or mindlessly scan back and forth without providing useful information. When an operator attempts to use a PTZ camera to obtain a high-resolution image of a target of interest, for example an intruder unlawfully crossing a perimeter, he or she must manually direct the camera to zoom in on the correct location. This process can be inaccurate and often too slow to catch the target. If a PTZ camera is given an automated scanning pattern to follow, for example sweeping back and forth along a perimeter fence line, human operators can easily lose interest and miss events that become harder to distinguish from the video's moving background. Ideally, the power and flexibility of moving PTZ cameras could be combined with the ability to automatically provide high-resolution imagery of targets of interest, while still providing wide-scale operational awareness for human operators and allowing for effective threat detection.